rhashtable: Use rcu_dereference_all and rcu_dereference_all_check

Add rcu_dereference_all and rcu_dereference_all_check so that
library code such as rhashtable can be used with any RCU variant.

As it stands rcu_dereference is used within rashtable, which
creates false-positive warnings if the user calls it from another
RCU context, such as preempt_disable().

Use the rcu_dereference_all and rcu_dereference_all_check calls
in rhashtable to suppress these warnings.

Also replace the rcu_dereference_raw calls in the list iterators
with rcu_dereference_all to uncover buggy calls.

Reported-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Author: herbertx

include/linux/rcupdate.h

@@ -713,6 +713,24 @@ do {									      \
 				(c) || rcu_read_lock_sched_held(), \
 				__rcu)
 
+/**
+ * rcu_dereference_all_check() - rcu_dereference_all with debug checking
+ * @p: The pointer to read, prior to dereferencing
+ * @c: The conditions under which the dereference will take place
+ *
+ * This is similar to rcu_dereference_check(), but allows protection
+ * by all forms of vanilla RCU readers, including preemption disabled,
+ * bh-disabled, and interrupt-disabled regions of code.  Note that "vanilla
+ * RCU" excludes SRCU and the various Tasks RCU flavors.  Please note
+ * that this macro should not be backported to any Linux-kernel version
+ * preceding v5.0 due to changes in synchronize_rcu() semantics prior
+ * to that version.
+ */
+#define rcu_dereference_all_check(p, c) \
+	__rcu_dereference_check((p), __UNIQUE_ID(rcu), \
+				(c) || rcu_read_lock_any_held(), \
+				__rcu)
+
 /*
  * The tracing infrastructure traces RCU (we want that), but unfortunately
  * some of the RCU checks causes tracing to lock up the system.
@@ -767,6 +785,14 @@ do {									      \
  */
 #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0)
 
+/**
+ * rcu_dereference_all() - fetch RCU-all-protected pointer for dereferencing
+ * @p: The pointer to read, prior to dereferencing
+ *
+ * Makes rcu_dereference_check() do the dirty work.
+ */
+#define rcu_dereference_all(p) rcu_dereference_all_check(p, 0)
+
 /**
  * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism
  * @p: The pointer to hand off

include/linux/rhashtable.h

@@ -272,13 +272,13 @@ struct rhash_lock_head __rcu **rht_bucket_nested_insert(
 	rcu_dereference_protected(p, lockdep_rht_mutex_is_held(ht))
 
 #define rht_dereference_rcu(p, ht) \
-	rcu_dereference_check(p, lockdep_rht_mutex_is_held(ht))
+	rcu_dereference_all_check(p, lockdep_rht_mutex_is_held(ht))
 
 #define rht_dereference_bucket(p, tbl, hash) \
 	rcu_dereference_protected(p, lockdep_rht_bucket_is_held(tbl, hash))
 
 #define rht_dereference_bucket_rcu(p, tbl, hash) \
-	rcu_dereference_check(p, lockdep_rht_bucket_is_held(tbl, hash))
+	rcu_dereference_all_check(p, lockdep_rht_bucket_is_held(tbl, hash))
 
 #define rht_entry(tpos, pos, member) \
 	({ tpos = container_of(pos, typeof(*tpos), member); 1; })
@@ -373,7 +373,7 @@ static inline struct rhash_head *__rht_ptr(
 static inline struct rhash_head *rht_ptr_rcu(
 	struct rhash_lock_head __rcu *const *bkt)
 {
-	return __rht_ptr(rcu_dereference(*bkt), bkt);
+	return __rht_ptr(rcu_dereference_all(*bkt), bkt);
 }
 
 static inline struct rhash_head *rht_ptr(
@@ -497,7 +497,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl,
 	for (({barrier(); }),						\
 	     pos = head;						\
 	     !rht_is_a_nulls(pos);					\
-	     pos = rcu_dereference_raw(pos->next))
+	     pos = rcu_dereference_all(pos->next))
 
 /**
  * rht_for_each_rcu - iterate over rcu hash chain
@@ -513,7 +513,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl,
 	for (({barrier(); }),					\
 	     pos = rht_ptr_rcu(rht_bucket(tbl, hash));		\
 	     !rht_is_a_nulls(pos);				\
-	     pos = rcu_dereference_raw(pos->next))
+	     pos = rcu_dereference_all(pos->next))
 
 /**
  * rht_for_each_entry_rcu_from - iterated over rcu hash chain from given head
@@ -560,7 +560,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl,
  * list returned by rhltable_lookup.
  */
 #define rhl_for_each_rcu(pos, list)					\
-	for (pos = list; pos; pos = rcu_dereference_raw(pos->next))
+	for (pos = list; pos; pos = rcu_dereference_all(pos->next))
 
 /**
  * rhl_for_each_entry_rcu - iterate over rcu hash table list of given type
@@ -574,7 +574,7 @@ static inline void rht_assign_unlock(struct bucket_table *tbl,
  */
 #define rhl_for_each_entry_rcu(tpos, pos, list, member)			\
 	for (pos = list; pos && rht_entry(tpos, pos, member);		\
-	     pos = rcu_dereference_raw(pos->next))
+	     pos = rcu_dereference_all(pos->next))
 
 static inline int rhashtable_compare(struct rhashtable_compare_arg *arg,
 				     const void *obj)